1. Field of the Invention
The present invention broadly relates to polymer composites containing graphitic nanotubes. More specifically, the present invention relates to polymer composites prepared from functionalized nanotubes and a monomer which reacts with functional sites on the nanotubes during in situ polymerization
2. Description of the Related Art
The advent of polymer composites containing carbon nanotubes has revolutionized the fields of materials science and materials engineering. These polymer composites are ⅙ the weight of steel but 50 to 100 or more times stronger than steel. As such, these polymer composites have found use in a variety of applications, from capacitors to electroconductive paint to electrodes. The demand for these materials has been great and improvements in their production are widely sought.
Methods of manufacturing composites containing carbon nanotubes begin with monomers that have already been polymerized to form a polymer matrix. Carbon nanotubes are added to the polymer matrix. Such methods and the products obtained are described, for example, in U.S. Pat. No. 5,643,502. U.S. Pat. No. 6,299,812 to Newman et al., describes the use of melt blowing and melt spinning to form composites containing carbon nanotubes. Carbon nanotubes are mixed with polymer pellets and the mixture is heated to a temperature greater than the melting point of the polymer. The liquefied mixture is extruded or spun, and then cooled to form a polymer composite. The carbon nanotubes are physically bonded to the polymer not chemically bonded.
Methods for crosslinking matrices of carbon nanotubes are described in U.S. Pat. No. 6,203,814 and U.S. patent application Ser. No. 08/812,856. The carbon nanotubes are first functionalized, e.g., by oxidation, and then reacted with crosslinking agents to form porous crosslinked nanotube structures having novel properties.
Studies have shown that the incorporation of monolayers of clay into polymer composites improve the properties of the composites, for example, the flexural strength and flexural modulus. The incorporation of clay into polymers also significantly enhances the barrier properties of certain polymers against compounds such as oxygen, nitrogen, carbon dioxide, water vapor, and gasoline. The use of clay in polymers can also increase the heat distortion temperature of the polymer.